Planetary excavator



PLANETARY EXCAVATOR Filed July 31, 1967 March 11, 1969 w. D. WATERMAN3,431,989

PLANETARY EXCAVATOR Filed July 31, 1967 Sheet 3 of 9 INVENTOR Q6 M4 4/s' D. Mnne/z/mu ATTORNEYS March 11, 1969 w. D. WATERMAN 3,431,989

PLANETARY EXCAVATOR Filed July 31, 1967 Sheet 4 of 9 I INVENTOR WM 1./6' Z; MTE'EMAA/ TQ NEY' March 1969 w. D. WATERMAN 3,431,989

PLANETARY EXCAVATOR Filed July 31, 1967 mvmozz l V/u/s .2 MTEQMAN March11, 1969 wQo. WATERMAN PLANETARY EXCAVATOR Sheet Filed July 31, 1967INVENTOR 1444; l5 .0. M/ATE'RMAIV T NEY? March 11, 1969 w. D. WATERMAN3,431,989

'PLANETARY EXCAVATOR f-iled July 51, 1967 Sheet 7 of 9 III I T NEYSINVENTOR March 11, 1969 w, WATERMAN 3,431,989

PLANETARY EXCAVATOR Filed July 31, 1967 INVENTOR Wad/5 0. WATEEMAA/ Amfw:

United States Patent 3,431,989 PLANETARY EXCAVATOR Willis D. Waterman,626 Max, Salina, Kans. 67401; Betty J 0 Waterman, administratrix of saidWillis D. Waterman, deceased Continuation-impart of application Ser. No.420,704, Dec. 23, 1964. This application July 31, 1967, Ser. No. 657,359U.S. Cl. 175-95 4 Claims Int. Cl. E21b 3/02, 9/24; F16h 55/34 ABSTRACTOF THE DISCLOSURE A rotary excavator.for drilling large diameter shaftsinto the earth and in which a pilot hole cutter and laterally extendedhole cutters are reversely driven by resilient drive members powered byreversible motors, and the laterally extended cutters move the cuttingsinto the pilot hole, for removal of the cuttings from the pilot holethrough a central pipe as a result of the high velocity flow of drillingfluid through the pipe to the surface of the earth.

This is a continuation-in-part of my copending application Ser. No.420,704, filed Dec. 23, 1964, for Planetary Excavator, and nowabandoned.

Summary of the invention A stationary pipe extending into the shaft inthe earth supports oppositely rotating cutter assemblies which aredriven by motors in the shaft and carried on the pipe. Each motorindividually drives an intermediate member which in turn drives bothcutter assemblies in opposite directions. The pipe carries cuttings fromthe shaft.

Description This invention relates to earth boring or drilling machines,more particularly to a device for the sinking of large-diameter sh-aftsfrom the surface either vertically or in a more-or-less horizontaldirection.

The excavation of chambers or passageways of from ten to twenty-fivefeet by a single machine without the use of explosives and/or extensivehand labor has long been desired by the mining and constructionindustries in reducing the costs of shafts, piers, and footings. Thisinvention for the first time makes available a rugged and practicablemachine capable of driving openings of this size rapidly, efiicientlyand economically.

It is an object of this invention to provide an excavator which can beattached to and operated from a conventional crane or which can operatebelow the usual drilling platform on the conventional drilling rig.

It is another object of this invention to provide a largediameterdrilling means which is capable of slow-to-rapid rotation and controlledchanges of direction clockwise and counterclockwise.

A further object of this invention is a large-diameter drilling machinewhich is readily and simply adjusted for a substantial range of holesizes.

Still another object of the invention is to provide a rugged and durableassembly for driving the cutting elements of a large diameter drillingmachine in an environment of drilling fluid which is employed to carrythe cuttings from the hole, the driving assembly including resilientdrive and driven members coengaged with one another and confined infrictional coengagement by a surrounding ring. The drive assembly beingsupported in the hole by a motor mount having motors which drive certainof the resilient drive elements, the motor mount being held againstreactive rotation by a pipe or conduit leading to the bottom of the holeand through which drilling fluid is caused to flow for the purpose ofcarrying cuttings ice upwardly through the pipe. In the use of theapparatus in the environment of the drilling fluid, which is inherentlyabrasive, an advantage results in respect of the increased frictiondrive capacity of the resilient drive members caused by the abrasiveparticles in the drilling fluid; whereas, in the case of the usual geardrives the presence of abrasive particles is detrimental.

Another object of the invention is to provide a drive mechanism in alarge diameter drilling machine wherein resilient drive and drivenmembers are employed for effecting rotation of the cutting elements,such resilient drive-and driven members being capable of absorbing heavyshock loads so as to prevent damage to the drilling apparatus, and beingcapable of compensating for unequal torque loads which are inherent inthe operation of large diameter drilling machines, notwithstandingefforts made in accordance with the invention for equalizing torqueloads. 'In the latter instance, it is a further object of the inventionto provide resilient drive and driven members which are substantiallyarranged as planetary drive elements including a sun member which isrelatively large and which is adapted to drive a centrally locatedportion of the cutting elements in one direction, while correspondinglylarge planet members coengaged with the sun member and within a ringmember are adapted to drive an outer portion of the cutter elements, inthe other direction, so that the work load resulting from operation ofthe drilling apparatus is substantially equally distributed or balanced.

Still another object of the invention is to provide a large diameterdrilling machine, the cutting elements of which include a pilot cutterfor cutting a pilot hole in advance of the main hole, the other cutters,adapted to drill the main hole, being arranged to move cuttings into thepilot hole as drilling progresses, and a conduit being provided andleading from the pilot hole to the surface of the earth so that drillingfluid filling the hole may be pumped from the conduit from the pilothole so as to efiiciently remove cuttings as the drilling progresses.

These and other objects vw'll be readily apparent from the followingdescription and appended drawings in which:

FIGURE 1 shows this large-diameter drill mounted on a crane;

FIGURE 2 is an enlarged view of the torque-arm assembly along the line2-2 of FIGURE 1;

FIGURE 3 is an enlarged vertical view, partly in section, of theplanetary driving mechanism and cutter assembly;

FIGURE 4 is a horizontal view, partly in section of the drive assembly,taken along the line 4-4 of FIGURE 3;

FIGURE 5 is a horizontal view, partly in section, of the cutter support,taken along the line 5-5 of FIG- URE 3;

FIGURE 6 is a horizontal view, partly in section, of the cutterassembly, taken along the line 66 of FIG- URE 3;

FIGURE 7 is an alternate form of cutter for use in harder formations;

FIGURE 8 is an enlarged vertical sectional view of the sun wheel andassociated structure;

FIGURE 9 is a horizontal view of the upper roller and guide assemblytaken along the line 9-9 of FIGURE 8;

FIGURE 10 is a view partly in vertical section and partly in elevationillustrating a modified cutter assembly;

FIGURE 11 is a view in transverse section on a reduced scale, as takenon the line 1111 of FIGURE 10;

FIGURE 12 is a view in transverse section on a reduced scale, as takenon the line 12-12 of FIGURE 10.

Referring more particularly to FIGURE 1, there is shown more-or-lessdiagrammatically a crane 200, having a boom with associated guy andcontrol cables, designated by the numeral 12. The crane is provided withsuitable transport and support means 13 for moving it to the drillingsite and holding it in position during the drilling operation. A cable14 paid out from a drum, not shown, in the control cabin of the craneand passing over the sheaves 15 at the upper end of boom 12 is providedwith a hook 16. Depending from hook 16 is a cable spacer 11 and aplurality of cables 17 which are attached to the lifting ring 18 on theupper part of the driving and cutting assembly 300, as shown in moredetail in FIGURE 3. Separately controlled cable 70 passing over sheave69 provides for adding to or removing sections of pipe from the drillstring in the usual manner.

Rigidly attached to crane 200, and extending outwardly thereof is atorque-arm assembly 20. As shown in FIG. 2 assembly 20 may be aframework formed of two members 21, each suitably attached to the craneat the inner ends and provided with an enlarged sleeve 22 transverselythereof at the outer end. Between the sleeves 22, there is a kelly 23adapted to be disposed within a holding bushing 23a, and also adapted tobe connected to a length of pipe 28. On either side of the kelly bushing23a, there is attached a pipe 24 each of which is rotatably fitted atits outer side, within one of the sleeves 22. A third pipe 25 extendsoutwardly from the kelly, and is provided at its end with two braces 26,which are rigidly attached to pipes 24 near sleeves 22 substantially asshown. This subassembly including the kelly bushing is thus a rigid unitwhich is pivotally mounted in sleeves 22 so that it is capable oflimited movement in relation to pipes 21. These latter may be furthersupported by cables 27 suitably attached to boom 12. The kelly 23 andassociated assembly serve to hold the pipe 28 securely against rotativemovement due to the rotative forces applied thereto by the planetarydrive assembly, as described hereinafter, while allowing sliding axialmovement of the kelly 23 and attached pipe 28 during drillingoperations. Although members 21, 24, 25 and 26 are shown as pipes, whichare preferred for most installations they may be rods or otherstructural shapes with the desired strength and rigidity.

Referring now to FIGURE 3, at its lower end the pipe 28 is attached tothe drive and cutting assembly 300 by conventional fittings designatedgenerally by the numeral 29, and adapted to accommodate fluid flow.Beneath the lifting ring 18 and integral therewith are a plurality ofmotor mount beams 30, arranged in pairs, each pair supporting a motor31.

In the preferred form of large bore excavator, motors 31 are reversiblehydraulic motors being supplied with hydraulic fluid under pressurethrough hoses 58 from a compressor system 59 in the conventional manner.Provision, of course, is made for extending hoses 58 as required withthe increasing depth of hole.

A shaft 32 extends downwardly from each motor 31 and carries at itslower end a wheel 33. Preferably, each wheel 33 is the dual rim typewith a pair of resilient tires 34 mounted thereon. Tires 34 are ofrubber or other elastomer suitable for maintaining friction drive. It ispreferred that these tires be pneumatic, such as are used on heavy-dutytrucks, but solid or semisolid tires may be used in some installations.Pneumatic tires may be filled with liquid instead of air or other gas ifdesired.

As shown in FIGURES 3 and 4, there are six such motor and wheelassemblies, equally spaced about the drill pipe. Surrounding these motorand wheel assemblies is a circular ring or drive shell 35, extendingupwardly from a horizontal ring plate 36. Ring plate 36 may be made of aplurality of arcuate sections for ease of fabrication and assembly.Shell 35 may also be in sections for ease of assembly and also tofacilitate servicing of the several wheels 33. To reduce the weight andalso to facilitate the fabrication, drive shell 35 preferably consistsof an inner shell 35a and an outer shell 35b with a plurality of rods orpipes 65 extending vertically between them. Extending radially inwardlyfrom ring plate 36 are a plurality of pipes 37 which are attached attheir inner ends to a lower sleeve 38, which extends about the lower endof pipe 28 for rotation thereabout, as will be hereinafter described.The spaces between the several pipes 37 may be covered by a plurality ofsector-shaped deck plates 39. Supporting flanges 40 for deck plates 39are welded or otherwise affixed to radial pipes 37.

As shown in FIGURES 3, 5 and 6, pipes 37 form the upper elements of thecutter support assembly, other elements of which, designated as 37A,extend downwardly from horizontal pipes 37, are provided with fittings41 for attachment of the cutter assemblies 350A, 350B. The diameter ofthe excavation is largely controlled by the over-all length of cutterassemblies 350A, 350B. In the preferred embodiment the excavator iscapable of driving excavations having a diameter varying from about 10/2 feet to about 25 feet.

The supporting framework formed of the pipes 37 and 37A, may be furtherbraced by the rods 66, which may be adjusted by turnbuckles, not shown,or other conventional means.

Means are provided for supporting the abovementioned sleeve 38 forrotation about the pipe 28, such supporting means in the illustrativeembodiment essentially hanging the sleeve 38, and thus ring 35, from themotor mounting means or beams 30, the ring 35 thereby also beingrevolvable about the pipe 28.

Referring more particularly to FIGURE 8, the lower sleeve 38, to whichare attached radial arms 37, is provided at its lower end with anoutwardly extending flange 42. Roller members 43 on the lower rollerguide assembly 44 at the lower section of a cylindrical member 45provide support for sleeve 38 and permit rotation thereof with a minimumof friction. As shown in enlarged detail in FIGURE 8, tubular member 45may be of sectional construction and may be flanged at its upper end 46rotatably supported by roller members 48 of roller guide assemblies 47.These assemblies 47 are mounted on, as by welding or the like, anddepend from the lower side of motor mount beams 30.

Thus, the tubular member 45 is rotatable relative to the pipe 28, andring 35 is rotatable relative to tubular member 45. A pair of innerwheels 49 are attached to the tubular member 45 and rotate therewith. Onthe rim of each wheel 49 is a resilient tire 50 of rubber or othersuitable elastomeric material which is in frictional engagement with oneof the tires 34 on the wheels 33. Tire 50, like tires 34, may be filledwith gas or liquid or may be solid or semi-solid, to suit the intendedservice.

As shown in FIGURE 8, pipe 28 and tubular member 45 may be in flangedsections of convenient lengths which are coupled at the flanges myheavy-duty bolts 51. However, other types of couplings used in oil fieldwork, such as quick-connecting clamps, may be substituted whereapplicable.

At the lower end of the tubular member 45 is mounted a pilot drill 52.FIGURE 1 shows, more or less diagrammatically a conventional tricone bitfor this purpose; however a drag bit or other bit of appropriate sizeand design may also be employed. As is customary the bit 52 will have ashank connectable to member 45 and capable of permitting the flow ofdrilling fluid and cuttings into the member 45. At the upper end ofdrill pipe 28, there is provided a coupling 53 for drilling fluid hose54. This hose, in turn, is connected to the suction side of pump 55which discharges into mud pit 56. Settled drilling fluid is returned tothe borehole through overflow pipe 57. Thus, as drilling progresses andresponsive to operation of pump 55. there will be a high velocity flowof drilling fluid through bit 52 into tubular member.45 and thenceupwardly through pipe 28, so that cuttings will be efficiently removedfrom the pilot hole.

In addition to the pilot drill 52 and radially extending cutterassemblies 350A, 350B, reamer cutters may be provided on the lower edgeof shell 35. These are spring-loaded so as to operatively engage theperiphery of the hole upon reverse rotation of the drill assembly thatis counter to drilling direction.

More particularly, the cutter assemblies 350A and 350B as thus fardescribed, may comprise, as best seen in FIGURES 3 and 6, a series ofcutter discs 61 disposed for rotation on shafts mounted on thesupporting structures as by the fittings 41 previously referred to, withthe shaft axis arranged in skewed relation to lines extended radially ofthe hole. By virtue of this arrangement of the cutter assemblies, eachof the cutter discs 61 is caused to drag across the bottom of the holeas the drilling progresses, whereby cuttings loosened by the earth willbe moved progressively toward and into the pilot hole formed by thepilot bit 52. Such progressive moving of the cuttings into the pilothole assures that the drilling fluid being pumped upwardly through thepipe 28 from the pilot hole can efliciently entrain the cuttings thereinand carry the cuttings to the top of the hole and into the pit 56. Thecuttings will settle out of the drilling fluid in the pit 56 and thedrilling fluid will return to the hole through the overflow 57 leadingfrom adjacent the top of pit 56 into the hole.

Referring to FIGURE 7, there is generally illustrated a modified form ofcutter assemblies adapted to be supported in the manner of the discassemblies 350A and 350B. These modified cutters designated 71 may beemployed for drilling through hard earth. These cutters 71 comprisecylindrical bodies capable of withstanding the forces involved when theyare caused to revolve in contact with the earth. Spaced longitudinallyof the cylinders are cutting edges which are composed of material suchas tungsten carbide formed as rings about the cylinder. Such aconstruction, since the different cutting edges traverse differentdistances as the cutting assemblies are rotated, causes a cutting actionsimilar to that of a rasp.

Operation It will now be understood that in the operation of thedrilling apparatus as thus far described, it will be lowered intoengagement with the earth by the crane 200 or such other suitablesupport as may be employed at the earths surface, and the hole as itprogresses will be maintained full of drilling fluid or mud inthje usualmanner. As the motors 31 are operated by the pumping of power fluidthereto from ,the pump 59,' each of the motors 31 will drive oneof thedriving wheels 33, the tires of which are in engagement with the ring 35which extends circumferentially in engagement with all of the wheels 33,so that as shown in FIGURE 4, as the wheels 33 are driven in a counterclockwise direction, counterclockwise rotation will be imparted to thering 35 at a speed dependent upon the diameter of the wheels 33 and thespeed at which they are driven. The motors 31 and the wheels 33 are heldagainst unitized revolution about the axis of the hole by virtue of thefact that the motor mounts 30 are connected through the pipe 28 to thekelly 23 which is fixed against rotation by the torque arm 20.

Each of the wheels 33 is further engaged with the central wheels 49fixed on the tubular member 45 which, as previously indicated, isadapted to revolve relative to the pipe 28 as well as relative to thering 35. Accordingly, the drive means may be characterized as planetaryin nature, the wheels 49 being the sun member of the planetary systemand the wheels 33 being the planetary members of the planetary system,which are adapted to drive the ring member 35.

Inasmuch as substantial loads are irnposed upon the drilling apparatusit is desirable that the work load be equalized by causing as nearly aspossible and practicable equal linear travel of the respective cutters.In part, this is accomplished in the present invention by employingcutting discs in the embodiment of FIGURE 1 which are progressivelysmaller from the outer disc toward the inner disc, forming a conicalrotary disc cutter assembly, each disc of which will travel the samedistance as it traverses the bottom of the hole. In addition, however,the work load is substantially equally distributed by causing rotationof the wheel 49 at a substantial rate, thus causing the pilot bit 52 torotate at a rate greater than the rate of rotation of the cutterassemblies 350A and 350B. It will be understood in this connection thatthis relative rate of rotation is accomplished by reason of the factthat planet members 33 are large in diameter and therefore, causesubstantial rotational speed of sun member or wheel 49.

Moreover, the tires 34 and 50 of the driving and driven wheels areconfined within the ring 35 in pressure loaded engagement with oneanother so as to assist in the frictional drive therebetween, and thepresence of abrasive particles, which would be objectionable in a geardrive, enhance the frictional drive between the resilient tires.

The sun member or wheel 49 will be caused to rotate in a clockwisedirection or opposite to the ring 35 so that the cutter assemblies 350Aand 350B will revolve about the hole axis in a counter clockwisedirection, while the pilot bit 52 revolves in a clockwise direction,thus tending to balance the torque and to reduce the holding effectrequired of the torque arm. 20.

As the hole progresses the cutters 350A and 350B, as previouslyindicated, will cause movement of the cuttings into the pilot hole, thelocation at which the drilling fluid filling the hole passes into theconduit leading to the pump 55. Thus, the velocity of the drilling fluidpassing into the pilot hole and into the conduit 28 will insureentrainmeht of the cuttings in the fluid stream so that they will beefliciently removed from the hole.

Referring now to FIGURES 10 through 12, there is illustrated amodification of the invention in which the power mechanism including theouter ring 35, central driven wheels 49 and intermediate drive wheels33, is the same as that previously described. In this modifiedconstruction, however, the cutting elements are somewhat differentlyarranged, and more particularly, a number of cutter discs which form thebottom of the hole are caused to revolve with and in the direction ofthe pilot bit 52, while other of such cutting discs revolve in theopposite direction.

As shown in FIGURE 10, the tubular member 45 is provided with a downwardextension connected to the pilot bit 52. Carried by the extension 145,suitable outwardly extended support arms 137a which are provided withfittings 141 on which are journaled the shafts of cutter assemblies1350a, each cutter assembly comprising a number of cutter discs 161, andas seen in FIGURE 12, there being a number of such assemblies spacedabout the tubular extension 145 and disposed with their axis skewedrelative to lines extended radially of the member 145. Braces 166extended between the support members 137a, as in the previouslydescribed embodiment, are adapted to rigidly interconnect the cutterassemblies. These cutter assemblies 1350a will, asseen in FIGURE 10, cutan intermediate section from the bottom of the hole above the pilot holeformed by the pilot bit 52, and inasmuch as the cutter assemblies areskewed as previously indicated, cuttings formed thereby will be caused,as shown by the arrows, to be moved into the pilot hole for purposes ofremoval by the drilling fluid.

In addition to the cutter assemblies 1350a, the cutting means includesadditional cutter assemblies 1350b which are supported on support arms237a mounted beneath the support members 37a on which the driven ring 35is mounted, whereby rotation of the ring 35 will impart rotation to thecutter assemblies 1350b. Like the cutter assemblies 1350a, the cutterassemblies 1350b include cutter discs 161 disposed upon a shaft which ismounted with its axis skewed relative to lines extending radially of thedrilling assembly. Thus, the cuttings formed by the cutters 1350b willbe caused to move inwardly into the intermediate hole section formed bythe cutters 1350a and with the cuttings formed by the latter cutterswill be caused to move into the pilot hole 52 for removal of thecuttings by the circulation of drilling fluid. In view of the foregoing,operation of the modified construction of FIG- URES 10-12 will beunderstood without further elaboration.

While preferred embodiments of the excavation and its mode of operationhave been described, it will be obvious to persons skilled in the artthat changes or alterations might be made without departing from theinvention in its broader aspects and, therefore, it is the aim of theappended claims to cover all such changes and modifications as fallwithin the true scope and spirit of this invention.

I claim:

1. In a rotary excavator for sinking a substantially vertical shaft inthe earth, the shaft containing a drilling fluid to support the wallsthereof, the combination of: a central non-rotary pipe extendingdownward into the shaft, a laterally extending support fixed to the pipebelow the level of the drilling fluid in the shaft, a centralelastomeric driven tire mounted to turn about the axis of said pipe, apilot bit, a tubular member connecting said pilot bit to said tire to bedriven therefrom to form a pilot hole in the bottom of the shaft, adrivering having an internal cylindrical surface, means mounting thedrive ring on said tubular member to turn about the axis of said pipe, acutter assembly connected to the drive ring for cutting the remainder ofthe bottom of the shaft, a plurality of elastomeric driving tiresrotatably mounted on said support and each frictionally contacting bothsaid central driven tire and said internal cylindrical surface of saiddrive ring, said driving tires serving to center said drive ring withrespect to said central driven tire, a plurality of motors fixed on saidsupport, one motor for turning each of said driving tires, respectively,whereby said pilot bit and said cutter assembly may be turned inopposite directions, and means for causing an upward flow of drillingfluid through said tubular member and said pipe to remove cuttings fromthe shaft.

2. In a rotary excavator for sinking a substantially vertical shaft inthe earth, the shaft containing a drilling fluid to support the wallsthereof, the combination of: a central non-rotary pipe extendingdownward into the shaft, a laterally extending support fixed to the pipebelow the level of the drilling fluid in the shaft, a central drivenelement mounted to turn about the axis of said pipe, a pilot bit, atubular member connecting said pilot bit to be driven from said elementto form a pilot hole in the bottom of the shaft, a drive ring elementencircling said central driven element, means mounting said ring elementto turn about the axis of said pipe, a cutter assembly driven by saidring element for cutting the remainder of the bottom of the shaft, saidcutter assembly including a plurality of rotary cutters each having itsaxis of rotation skewed in relation to a radius line of the pipe wherebycuttings loosened from the earth are moved progressively towards andinto the pilot hole, a plurality of interme- .diate driving elementsmounted on said support and each driving both said central drivenelement and said driven ring elements, a plurality of motors mounted onsaid support, one motor for turning each of said intermediate drivingelements respectively, whereby said pilot bit and said cutter assemblymay be turned in opposite directions, and means for causing an upwardflow of drilling fluid through said tubular member and said pipe toremove cuttings from the pilot hole.

3. In a rotary excavator for sinking a shaft in the earth, the shaftcontaining a drilling fluid to support the walls thereof, thecombination of: a central nonrotary pipe extending into the shaft,cutter means revolvable in said shaft, and power means supported on saidpipe beneath the level of drilling fluid in said shaft for driving saidcutter means, said cutter means including first cutter means revolvablydisposed about said pipe, second cutter means revolvably disposed aboutsaid pipe and within said first cutter means, said power means includinga drive ring connected to said first cutter means, a central drivemember connected to said second cutter means, intermediate drive membersfrictionally engaged with said drive ring and with said central drivemember, said power means also including individual motors each connectedto and driving one of the respective intermediate drive members, meansfor holding said intermediate drive members against revolution aboutsaid central drive member, and means for causing the flow of saiddrilling fluid upward through said pipe to remove cuttings from theshaft.

4. A rotary excavator as defined in claim 3, wherein the individualmotors are reversible, and wherein said cutter means includes reamingcutters having means for urging the same into engagement with the sidewall of said shaft upon rotation of said motors in one direction.

References Cited UNITED STATES PATENTS 902,517 10/1908 Wittich --104 X1,747,908 2/1930 Seifert 175-391 X 1,826,396 10/1931 Gault 1753192,105,091 1/1938 MacKay 17595 2,111,422 3/1938 Fawick 74216 X 2,384,3979/1945 Ramsay 175-319 X 2,766,978 10/ 1956 Robbins 175-319 X 3,024,8523/1962 Jewell 175319 X 3,185,226 5/1965 Robbins 175-102 FOREIGN PATENTS782,851 3/1935 France.

87,952 8/1896 Germany.

892,581 10/ 1953 Germany.

CHARLES E. OCONNELL, Primary Examiner,

IAN A. CALVERT, Assistant Examiner.

US. 01. X.R.

